My assumption is that people are productive in Rust mainly because of the ecosystem, just like Python programmers are because they can download so many ready-to-use parts. The great mashup languages.

The context of this thread is AI-assisted code. There's no "people" involved, the AI can reconstruct just the parts of the ecosystem that it needs as easily as it can use the ecosystem. That's one of the big sea changes with AI: a lot of the best practices we've developed for coding really focus on creating good user interfaces and abstraction boundaries for coders so we can work in teams and have reasonable PL ergonomics, but when there is no team and no human, many of those considerations disappear.